Grid sorting by shadow contours



Feb. 2, 1960 c, sc 51 2,923,197

GRID SORTING BY SHADOW CONTOURS Filed Aug. 11, 1955 FIG. I FIG.2 FIG. 3 FIG. 4

24 X Am INVENT OR CHARLES F. SCHEID ATTORNEY Uni S a e Page 1Q 2,923,197 GRID SORTING BY SHADOW CONTOURS Charles F. Scheid, Lock Haven, Pa., assignor, by mesne assignments, to Sylvania Electric Products Inc., Wilmington, Del., a corporation of Delaware Application August 11, 1955, Serial No. 527,693

1 Claim. (CI. 88-14) This invention relates to a sorting process and particularly to a process for sorting spiral wound line-up type grids in accordance with shadow contours.

In the manufacture of radio tubes of the beam power type such as types 6L6, 6CD6, 3535, it is desirable to have the number 1 or control grid and number 2 or screen grid within the tube so wound that the lateral wires on the number 1 grid shall be in alignment with the lateral wires of the number 2 grid to permit unrestricted flow of sheets of electrons from cathode to anode. In the usual process of manufacture of this type of tube, the tube elements are assembled into a mount including the grids, and after mount assembly the grids are lined up with respect to one another. However, in some instances, where the grids utilized for assembly may not be uniformly of the same number of turns per inch or where, due to malformation of the wires of one or both of the grids, it is impossible to line up the grids, there is a resulting loss of mounts which could have been avoided had it been possible for the grids to be inspected for desired line-up characteristics prior to assembly. This invention makes it possible to easily and quickly determine the geometrical characteristics of the grids prior to assembly within a mount thus making it possible to discard improper grids before assembly into a mount and avoiding needless expense in discarding entire mounts because of bad grid alignment.

In accordance with the principles of this invention, after grids have been wound, they are received one by one in pockets of a tray, the background color of which contrasts with the color of the wound wire. Then by oscillating the tray in front of an observer and about a horizontal axis, characteristic shadow areas will move across each wound grid. -It is by the inclination of these areas, their width, uniformity of width, and their straightness that geometrical characteristics of the grids may be determined. Removing from the tray those grids which display undesired characteristics in these shadow areas and replacing the grids with others with desired characteristics it is possible to obtain a tray full of grids which when assembled into a tube mount will give desired results in a beam power type tube.

For a fuller understanding of this invention, reference is made to the accompanying drawings in which:

Fig. l is a sketch showing the shadow area of an almost excellent wound grid.

Fig. 2 is a sketch showing the shadow area of a poorly wound grid.

Figs. 3 and 4 are sketches showing the shadow areas of other poorly wound grids.

Fig. 5 shows a grid tray, which may be used in the process, filled with grids.

Referring to the drawings with greater particularity, in Fig. 1 there is illustrated a grid with a shadow or moir area 12 approaching the ideal. This shadow or contour area is a parallax caused condition. When a grid of the line up type is wound, the laterals on one face of a grid cross the laterals on the opposite face causing a wide angle V-shaped space, when viewed perpendicularly of the 2,923,197 C l atelttedlj'eh. .2,196,Q

. laterals. This is so because the bottom laterals start from appears to progressively shift laterally along the grid because with the grid held in a fixed position, the angle of viewing the grid lateral crossovers changes as the line of sight moves along the grid. If, now, an operator holds a grid against a background contrasting in color with that of the grid, the V-shaped openings will collectively appear as an area inclined to the grid laterals and be in contrasting brightness with the remainder of the grid. If the background be black and the grid be some other color, the shadow area will be dark. If now the grid be rotated in front of the operator in a direction about a line parallel to a line joining the side rods, the shadow area will shift laterally due to apparent shifting of the cross over points of the grid laterals. This shifting or sweep of the area will show up irregularities in winding of the grid, particularly in spacing of the wires and in distortions in the laterals.

If, as for example is shown at 14 in Fig. 2, there be a number of cross over points unduly shifted to the left, a bump, such as 16, will appear. A certain degree of outrage of the bump as measured by the distance 18 may be tolerated. An excessive amount will cause poor performance in a line-up type of tube; therefore a grid having a large bump would be removed from amongst the remainder of the grids.

Fig. 3 shows a grid with a shadow area having a number of bumps 20 therein denoting several places with uneven pitched laterals along the grid. Fig. 4 shows a grid with a portion 22 of the shadow area thicker than other portions due to the change of angularity between front and grid laterals. It also shows a bad distortion of the grid at 24.

In actually carrying out the process, the grids are deposited one by one by a grid winding machine into a grid tray in individual pockets in the tray. A machine for doing this is described in an application filed by Stanley J. Gartner, Serial No. 423,391, filed April 15, 1954, now Patent 2,821,825. The tray 30, as shown in Fig. 5, has a number of pockets 32 designed to have deposited therein one or more grids, as determined by the setting of the machine. For the purpose of carrying out the process hereimthe machine would be set to cause only a single grid to be placed in a pocket.

In accordance with the process of this invention, an operator receives the trays and picks them up serially. The operator then holds each tray below the line of sight with the grid side rod substantially perpendicular to the body. The tray is then oscillated about an axis parallel with a line joining the two side rods and the appearances of the shadow area as they travel across the width of the grids noted. Preferably the oscillation is about a line parallel to a line perpendicular to and joining the side rods. Those grids with undesirable shadow areas are then removed and replaced by other grids known to have desirable geometrical characteristics. For the sake of clarity and simplicity, Fig. 5 of the drawings does not show the back grid laterals.

In an actual utilization of the process, the tray is black and contrasts very well with gold wire wound grids. It is contemplated utilizing grids of other color or making the pockets of trays other than black to secure a contrast between tray pocket and grid, should the grid not show up well against a black background.

Having thus described the invention, what is claimed is:

The method of demonstrating the character of grids each ofwhich has a helical winding about a pair of side rods, said method comprising placing thegrids in a support of a color contrasting to that of the helical winding mass-n91 cf the grids with all of the side rods in substantial parallelism, ill'iirninating all of the windings of the grids and the exposed underlying support, oscillating the support about an axis in the plane of thesupport and. perpendicular to the side rods to produce rnoir contours traversing each of the grids from side rod to the other, the moir contours resulting from said illuminating, and detecting the said moir contours.

References Cited in the file of this patent UNITED STATES PATENTS 1,424,556 Cooke Aug. 1, 1922 Luhn ...V Nov 10 1931 Boadwee et a1 Nov. 3, 1936 Jan-nan Sept. 24, 1946 Budney Sept. 4, 1956 FOREIGN PATENTS France Apr. 18, 1951 Great Britain ",2. July 20, 1933 

